HALIFAX - A Cougar helicopter aborted a flight to an offshore vessel Wednesday and made an emergency landing in Halifax after an onboard safety system indicated there were particles in the chopper's oil.

An official with the Newfoundland-based company said a chip indicator on the Sikorsky S-92 sensed there were lose fragments of material in the oil, which can cause problems in the main gearbox.

Hank Williams, base operations manager for Cougar Helicopters, said the crew immediately reduced power to lessen the stress on the engines, and diverted back to Halifax at about 10 a.m. AT.

"We got about 55 to 60 nautical miles into that flight and the pilot had an indicator light," Williams said at the Halifax airport where the helicopter was being examined by a maintenance team.

"What they did was reduce power - both engines were available to them and running at all times."

The two crew and 15 passengers made an emergency landing in Halifax about 30 minutes later, according to protocol, and were all in good condition.

The helicopter was heading to a vessel working on the Deep Panuke natural gas pipeline about 145 kilometres offshore.

The Sikorsky is the same model as a Cougar S-92 that was involved in a fatal crash off Newfoundland last March in which 17 people died as they were being ferried to an oil rig.

Williams said there are five such indicators around the oil circulation system that can pick up small fragments of metal with a magnet, and when enough accumulates, it sets off a warning light in the cockpit.

He said they've had about three similar occurrences over the last year in which they've had to return to base because an indicator has warned of a potential problem.

"You have to understand the gearbox on an aircraft is all moving metal so eventually over time they will always make a little bit of metal," Williams said.

He said he hadn't yet talked to maintenance crews that were examining the aircraft, but "first indications are that it's nothing serious."